1. Field of the Invention
The present invention relates to a high efficiency erase head and, more particularly, to an AC erase head which requires considerably less power to erase long wavelength signals from magnetic tape than similar erase heads used heretofore.
2. Description of the Prior Art
One of the single most important parts of a magnetic tape recording and playback system is the transducer which converts electrical signals to magnetic signals and back to electrical signals. These transducers are typically referred to as "heads". Heads are used for recording information on magnetic tape, reading information from magnetic tape and erasing prerecorded signals on magnetic tape. The present invention is conconcerned with the problems associated with erase heads.
There are a number of different types of magnetic heads that have been developed for use as an erase head in an instrumentation magnetic recording system. One commonly used type includes a pair of opposed, generally C-shaped pole pieces positioned in facing relationship, with a gap between first ends of the pole pieces, each pole piece being formed from a ferrite material and having a coil wound therearound. A conductive gap material is bonded on opposite sides of a ferrite gap spacer and this subassembly (the gap spacer with the gap material on opposite sides thereof) is placed between the first ends of the pole pieces. The other ends of the pole pieces are in contact with each other to complete the path for the magnetic lines of flux. The two pole pieces are then bonded together by injecting a potting compound into the inner cavity. The completed assembly forms a ferrite core module which is then inserted between metal half brackets which are secured together by retaining screws. Additional potting compound is typically injected into cavities in each half bracket to better secure the ferrite core module therein. It should be observed that only the ferrite core module concerns itself with the erasure of magnetic tape and the metal half brackets serve as a means of support and provide mounting capability for the head.
When a high frequency alternating current is applied to the windings on the ferrite pole pieces, a magnetic field is set up such as to cause flux to flow easily through the high permeability pole pieces. The non-magnetic, conductive gap material on the opposite sides of the gap spacer begin to generate eddy currents which oppose the flux path from one pole piece to the other. The result is that the flux at the gaps is shunted upwardly into the tape and principles of recording or erasure take place. In the above described construction, there are two gaps which conduct flux into the tape although a single gap or three or more gaps can be used.
AC erase heads require considerably more power to erase long wavelength signals from magnetic tape than do record heads which record similar wavelengths on the tape. As a result, a highly efficient AC erase head will attempt to insure confinement of the flux lines through the core structure to the gap area where they are shunted upwardly into the magnetic tape. In spite of previous attempts to increase the efficiency of AC erase heads, considerable power is typically required. This presents at least two problems. The first is the necessity to provide the power and the second is that the applied power causes heating of the erase head and the necessity of finding a means for dissipating such heat.